Blodgett-Langmuir transfer

Monolayers can be transferred layer-by-layer onto solid substrates such as silicon wafers or mica by the Langmuir-Blodgett2 (LB) technique [620,621] (reviews Refs. [622-625]). This is shown schematically in Fig. 13.13. 

The lipid is dissolved in a solvent which evaporates easily and is not miscible with water (usually chloroform, CHCI3). After the hydrophilic solid substrate has been moved into the pure water subphase, drops of the lipid-containing solvent are set carefully onto the water surface between the movable barriers by a syringe ( spreading ). After solvent evaporation the monolayer is compressed to the desired pressure (usually some 20-40 mN/m, in the LC phase). 

The hydrophilic substrate is moved continuously out of the water subphase at constant film pressure. During the upstroke the monolayer is transferred onto the wafer with the headgroups oriented towards the solid substrate and the alkyl chains exposed to the air. This renders the hydrophilic solid surface with a high surface energy of about 50 mN/m (for silicon) to a hydrophobic surface with a relatively low surface energy in the range of 20-30 mN/m. 

By a consecutive downstroke into the subphase through the floating monolayer a second layer can be transferred, with the alkyl chains oriented towards the solid substrate in a tail-to-tail configuration. 

By another upstroke a third layer is transferred with the headgroups oriented towards each other ( head-to-head ) and the hydrocarbon chains are exposed to the air. 

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The artificial lipid bilayer is often prepared via the vesicle-fusion method [8]. In the vesicle fusion process, immersing a solid substrate in a vesicle dispersion solution induces adsorption and rupture of the vesicles on the substrate, which yields a planar and continuous lipid bilayer structure (Figure 13.1) [9]. The Langmuir-Blodgett transfer process is also a useful method [10]. These artificial lipid bilayers can support various biomolecules [11-16]. However, we have to take care because some transmembrane proteins incorporated in these artificial lipid bilayers interact directly with the substrate surface due to a lack of sufficient space between the bilayer and the substrate. This alters the native properties of the proteins and prohibits free diffusion in the lipid bilayer [17[. To avoid this undesirable situation, polymer-supported bilayers [7, 18, 19] or tethered bilayers [20, 21] are used. 

Figure 13.13 Langmuir-Blodgett transfer of organic monomolecular layers from water onto solid substrates.

Monolayers can be formed on electrode surfaces by irreversible adsorption or covalent attachment, or, in the form of organized assemblies, by Langmuir-Blodgett transfer and self-assembly techniques. 

Fig. 5. Schematic of Langmuir-Blodgett transfers. The gray circles represent the hydrophilic head groups, and the thin black lines represent the alkyl chains. The molecules have been spread on an aqueous subphase, (a) A hydrophilic substrate is being withdrawn from the dipping well and is attracting the hydrophihc head groups that drive the film transfer, (b) A hydrophobic substrate is being pushed down through the monolayer. The alkyl chains are transferred, and the monolayer is pulled off the surface by hydrophobic interactions.

Several techniques have emerged for creating more ordered two- and three-dimensional assemblies of nanoparticles including Langmuir-Blodgett transfer, layer-by-layer assembly, and diblock copolymer lithography. These techniques are suitable for assembling MNPs with well-ordered nanostructures. A complete discussion of these techniques is beyond the scope of this chapter, but these topics have been extensively reviewed. ... 

Langmuir-Blodgett transfer A Langmuir film transferred to a substrate by moving it perpendicular to the film. 

Surface Modification by Langmuir-Blodgett Transfer of 8CB and Chemisorption of DMOAP... 

A weaker adsorption of the first layer is observed on substrates modified by Langmuir-Blodgett transfer of a monolayer and trilayer of 8CB, respectively (Fig. 7b). 

A number of other systems have been shown to be suitable for multilayer build-up by the ESA, like charged latex nanospheres [50,199,285-287] or metallo-supramolecular complexes [288-290]. ESA has also been combined with Langmuir-Blodgett transfer [291-294], and even superlattice films have been produced. 

Schematic depiction of two methods to prepare polymer brushes via Langmuir-Blodgett transfer, (a) LB transfer of amphiphilic diblock copolymers to a hydrophobic interface, (b) LB transfer of a lipid monolayer, of which some lipids are cormected to a hydrophilic polymer chain, to a surface coated with an opposite lipid monolayer.

Lvov, Y, Essler, F. and Decher, G., Combination of polycation/polyanion self-assembly and Langmuir-Blodgett transfer for the construction of superlattice films. JPhys Chem, 1993. 97 p. 13773-13777. 

Claro PCDS, Coustet ME, Diaz C, Maza E, Cortizo MS, Requejo EG, Pietrasanta LI, Ceolin M, Azzaroni O (2013) Self-assembly of PBzMA-b-PDMAEMA diblock copolymer films at the air-water interface and deposition on solid substrates via Langmuir-Blodgett transfer. Soft Matter 9 10899-10912... 

Figure 10.6 Attractive force measured with the SFA between two mica surfaces that had been coated with the double-chain cationic surfactant N-(a-trimethylammonioacetyl)-0, Cf-bis (1H, 1 H,2H,2H-perfluorodecyl)- L-glutamate chloride by Langmuir-Blodgett transfer [1190]. Force curves were recorded with different...

Figure 1. Schematic diagram illustrating Langmuir-Blodgett transfer under potentiostatic conditions. A gold-coated glass slide is acting as a working electrode in a three-electrode potentiostatic circuit. Below, an inset shows the pattern of the vapor deposited gold film. The central rectangular area (A = 0.20 cm ) is coated with an LB monolayer as the substrate is withdrawn from the subphase. The two lines mark the initial and the final position of the water meniscus in the LB experiments.

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